Delete ALL characters, etc. between two words

I have a problem that makes me want to rip out what little hair I have left.

I received a bunch of blogs and consolidated them into one InDesign (CS3) file, and now I'm trying to format them for easier reading in one file. However, there are some relatively common elements to each one that I'd like to delete using Grep.

I'd like to remove EVERY character, space, digit, space, and whatnot, between the words "Sent" and "PDT". Note that there could be a more than a hundred characters between those two elements. Please help. It would make this project so much easier, and would help with future problems of this type.

Like I said, I'm a noob. I only first heard of sed yesterday while searching for the same solution, and have no idea how to access it.

I'm more of a DTP guy (got my start with PageMaker) and have been noodling around with scripting with Automator and Applescript for the past year or so. If I could set this up in InDesign using the GREP command, that would be great, but if I'm stuck using sed instead (so to speak) that would be fine. I just don't know how to use it and could use some more basic instruction. For instance, is it used through Terminal? Thanks for your response, by the way.

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